Help with AD sound system.

[wibas]

I have an in dash KC Harris KHE-300. It has 200 watt(4x50) output with a dual 4ohm front in dash speaker. I think I want to add either 2 6x9 or 4x10 speakers plus a sub woofer. I probable need some kind of an amp to drive the rear speakers and sub. I'm not sure where to start. I'm working on 1952 GMC with bucket seats. I want to speakers where the gas tank was. The sub needs to be in a truck enclosure. Anybody got any ideas? Thanks. Merry Christmas!